Hardness and Wear Characteristics of Novel Zirconia-Based PICN

Objectives: The aim of this study was to investigate the mechanical properties, particularly hardness and wear characteristics, of a novel zirconia-based PICN material with the potential for use in tooth restorative applications.
Methods: A zirconia slurry was formulated by dispersing yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP, procured from TOSOH) particles in distilled water. The slurry was subsequently poured into a mold to dry, yielding a green body. Post-drying, the green body was sintered at 1200°C, producing a porous zirconia. This was immersed in a resin monomer mixture and heat-polymerized at 80°C for 24 h. The resultant zirconia-based PICN (labeled EXP) was subjected to Vickers hardness and two-body wear tests. Commercially available materials, including CAD/CAM resin composite (Cerasmart, GC; CS), silicate glass-based PICN (ENAMIC, VITA; VE), and zirconia (e.max ZirCAD; ZIR), served as the reference samples. Data were statistically analyzed using one-way ANOVA, accompanied by Tukey’s post-hoc test (p < 0.05).
Results: The Vickers hardness of EXP was found to be 440±51 VHN, which was higher than the hardness of VE (193±14 VHN) and CS (76±8 VHN). However, the hardness of EXP was lower than that of ZIR (1051±192 VHN), but it was noted that the hardness of EXP was close to that of human enamel. In terms of wear, all materials, except for ZIR, exhibited an increase in wear as the number of wear cycles increased. After 50,000 wear cycles, the volumetric wear loss of EXP was comparable to those of VE (0.24±0.03 mm³) and CS (0.27±0.01mm³) while higher than that of ZIR (approximately zero).
Conclusions: It was found that the zirconia-based PICN demonstrated mechanical compatibility with human enamel in terms of hardness. Additionally, it exhibited similar wear durability to resin composite and silicate glass-based PICN.